Portable or mobile devices originally introduced as mobile phones or electronic agendas become more and more ubiquitous. As the processing power of their internal processors grows and equally the bandwidth for communication with stationary processors, such portable devices take on more and more the role of multi-purpose tools available to consumers and specialist users alike.
It has been recognized that portable devices can benefit from the presence of sensors capable of providing a chemical analysis of materials brought into contact or the vicinity of the device. Whilst there are many possible applications for such sensors, it suffices to consider for example the analysis of air surrounding the portable device. Such an analysis can be useful for multiple purposes such as testing for hazardous gases, breath analysis for general medical purposes or driving fitness, and the like.
Specialized devices for testing the breath for ketones are well known and can for example be found in the United States patent application 2008/0077037.
Recently progress towards portable devices have been reported in the NTT DOCOMO Technical Journal Vol. 14, No. 1,51-57. However, the described device remains a specialized equipment, which can communicated with remote servers only via a separate mobile phone.
Acetone detection integrated in a mobile device is briefly referred to in the U.S. Pat. No. 8,280,436 B2 purporting to use infrared spectrophotometers, electrochemical fuel cells or other gas analysers. The acetone is used as an indicator for the blood alcohol levels of the user.
In clinical studies such as S. K. Kundu et al., “Breath Acetone Analyzer: Diagnostic Tool to Monitor Dietary Fat Loss” CLINICAL CHEMISTRY, Vol. 39, No. 1, 1993, 87-92 correlations have been suggested between acetone measurements and fat loss.
It has further been recognized that devices which receive a mixture of breath and surrounding air require compensation for the dilution caused by the air The compensation can done using parallel humidity, chemical (e.g. CO2, O2 concentrations) or temperature measurements using for example optical or other methods.
Humidity sensors for mobile applications are described for example in the published United States patent application US 2012/231841 and ways of manufacturing miniaturized sensors as MEMS devices with a CMOS connections and circuitry are described for example in the published international patent applications WO 2012/100362 A1 or WO 95/19563.
In view of the prior art it is an object of the present invention to improve general purpose portable devices with an integrated ketone analyzer sufficiently small to fit within the housing of such devices.